The novel begins in the Shire, as Frodo Baggins inherits the Ring from Bilbo; both are unaware of its origins. Gandalf the Grey, a wizard, learns of the Ring's history and advises Frodo to take the Ring away from the Shire. Frodo leaves, taking his gardener and friend, Samwise ("Sam") Gamgee, and two cousins, Meriadoc ("Merry") Brandybuck and Peregrin ("Pippin") Took, to help him. They encounter the Ringwraiths whilst still in the Shire, but shake off the pursuit by cutting through the Old Forest, where they are aided by the enigmatic and powerful character Tom Bombadil. After passing the Barrow-downs with Tom's help, they stop for a night in the town of Bree. There they meet Aragorn who calls himself "Strider" and joins them as guide and protector. They leave Bree after narrowly escaping an attack by the Ringwraiths. On the journey to Rivendell, Frodo is wounded on Weathertop by the Ringwraiths, who continue in close pursuit. At the Ford of Bruinen, Frodo and the others are rescued, as flood waters controlled by Elrond, master of Rivendell, rise up and overwhelm the Ringwraiths, sweeping them away.
Frodo recovers under the care of Elrond. The Council of Elrond reveals much significant history about Sauron and the Ring, plus the news that Gollum has escaped from Mirkwood and Sauron has corrupted the wizard Saruman. The Council decides that the threat of Sauron is too great and that the best course of action is to destroy the Ring. This can be done only by returning it to the Cracks of Doom in Mordor, where it was forged. Frodo volunteers to take the Ring, and a "Fellowship of the Ring" is chosen to accompany him. The Fellowship is composed of nine members, to set out against the nine Ringwraiths. Along with Frodo, Sam, Merry and Pippin go Aragorn, Gandalf, Gimli - the son of Glóin, one of the dwarves that accompanied Bilbo on his quest, Legolas - an elf from the woodland realm of Mirkwood, and a man - Boromir son of the Steward Denethor from the realm of Gondor.
The company is forced to travel through the Mines of Moria, where they are attacked by Orcs. Gandalf fights a Balrog and falls into a deep chasm; the others escape, and take refuge in the Elven forest of Lothlórien. With boats and gifts from the Lady Galadriel, the company then travel down the great River Anduin to Amon Hen. There Boromir succumbs to the lure of the Ring and attempts to take it from Frodo, who breaks from the Fellowship and continues the trek to Mordor accompanied only by Sam.
Orcs sent by Saruman and Sauron attack, killing Boromir and kidnapping Merry and Pippin. Aragorn, Gimli and Legolas pursue the Orcs into Rohan. Merry and Pippin escape when the Orcs are slain by the Rohirrim and find themselves in Fangorn forest where they befriend the tree-like Ents. Aragorn, Gimli and Legolas encounter Gandalf, who is now "Gandalf the White", in Fangorn forest. Gandalf travels with them to rouse Théoden, King of Rohan, and the Rohirrim to take a stand against Saruman's armies. Théoden initially decides to fight Saruman's forces at the fords of the river Isen, but upon hearing that those who defended that area have retreated to the fortress of Helm's Deep, he decides to make his stand there. Gandalf rides to Isengard; while Legolas, Gimli and Aragorn travel with Théoden and his nephew ?omer. After much fighting at Helm's Deep, the Rohirrim mount a final charge and drive the Orcs into a forest of Huorns raised by the Ents, where they disappear, just as Gandalf arrives.
The Ents destroy Saruman's remaining forces in Isengard. Gandalf, Théoden and the others arrive at Isengard. Saruman, however, refuses to see the error of his ways, and Gandalf strips him of his rank and most of his powers, and the Ents imprison him there. Pippin looks into a palantír, a seeing-stone that Sauron had used to communicate with Saruman, unknowingly leading Sauron to think that Saruman has captured the Ring-bearer. Gandalf takes Pippin to Gondor to remove him from the temptation of the palantír.
Frodo and Sam capture Gollum and force him to guide them to Mordor. They travel a long and hard road, briefly aided by Boromir's brother, Faramir. Gollum betrays Frodo by leading him to the great spider Shelob in the tunnels of Cirith Ungol. Frodo is left unconscious by Shelob's bite, but Sam fights her off using Sting and the vial of light from ?arendil's star — one of the Lady Galadriel's gifts. Sam, believing Frodo dead, takes the Ring, and Frodo is carried to the tower of Cirith Ungol by Orcs.
Sauron begins his military assault upon Gondor, with the Witch-king of Angmar, greatest of the nine Ringwraiths, commanding Sauron's armies in the battle.
Gandalf arrives at the City of Minas Tirith in Gondor with Pippin, to alert the Steward of the impending attack. Pippin becomes one of the Guards of the Citadel of Minas Tirith, while Merry, who has remained in Rohan, becomes esquire to its King. Aragorn takes Gimli and Legolas through the Paths of the Dead where he raises an undead army of oath-breakers. These help him to defeat the armies of the Corsairs of Umbar in southern Gondor, enabling the region's forces to sail to the aid of Minas Tirith in its Siege.
Denethor, Ruling Steward of Gondor, believing both his sons are dead and under the influence of Sauron through another palantír, loses hope and commits suicide. But, with the timely aid of Rohan's cavalry and Aragorn's reinforcements, a significant portion of Sauron's army is defeated. King Théoden dies in the battle, but the Lord of the Nazg?l, the Witch-king of Angmar, is slain by ?owyn and Merry.
Sam rescues Frodo from captivity, and they make their way through Mordor. After many hardships, they reach Mount Doom. Meanwhile, in the climactic battle at the Black Gate of Mordor, the vastly-outnumbered alliance of Gondor and Rohan fight desperately against Sauron's armies, with the intent of diverting Sauron's attention away from Mount Doom, which Frodo must reach in order to destroy the Ring.
At the edge of the Cracks of Doom, Frodo falls to the lure of the Ring, and claims it for himself. He puts the Ring on his finger. Gollum struggles with Frodo for the Ring, and bites off Frodo's finger, Ring and all; but in so doing he falls into the fire, taking the Ring with him. The Ring is thus unmade the only way it can be: in the same fire in which it was forged. In the instant of its destruction, Sauron perishes, his armies fall apart, the Dark Tower crumbles into dust, the Ringwraiths disintegrate, and the war of the Ring ends.
Amid the victory celebrations, Aragorn is crowned King of Gondor, and he marries Arwen, the daughter of Elrond and his long time love.
Saruman escapes his captivity in Orthanc and enslaves the Shire, but the returning Hobbits raise a rebellion and overthrow him in The Battle of Bywater. Saruman's throat is slit by Wormtongue, his former servant, who is in turn felled with arrows from Hobbit archers. Merry and Pippin are acclaimed as heroes. Sam uses his gifts from Galadriel to restore and beautify the Shire, and marries Rosie Cotton. Frodo remains wounded in body and spirit and, accompanied by Bilbo and Gandalf, sails from the Grey Havens west over the Sea to the Undying Lands to find peace. Sam returns home, and eventually becomes Mayor of the Shire. After Rosie's death, Sam leaves the Red Book of Westmarch with his daughter and crosses west over the Sea, the last of the Ring-bearers
故事發生在中東的歷史事件的背景下進行紮實。在這些之前，小說的開始並不知道歷史的主角，並在魔索倫鍛造執政環。在戰鬥中擊敗索倫，埃西鐸切斷索倫的戒指並聲稱自己了。埃西鐸是後來死於獸人，而在環江安杜因丟失。
兩千多年後，Déagol找到戒指，而他的堂兄Sméagol（或咕嚕捕魚），然後殺死誰的環Déagol。 Sméagol保持近五百年前失去它的戒指，於是比爾博巴金斯發現它。與此同時，索倫重新占領魔。咕嚕列出的環搜索，但近魔捕獲和索倫，審問誰
它的發現學習的比爾博。咕嚕設置松散但由阿拉貢，埃西鐸的繼承人，和精靈關在幽暗密林落網。與此同時，他提出了索倫發出可怕的公務員，戒靈，抓住環。
這本小說開始在希雷，為佛羅多繼承的比爾博環;都是不知道它的起源。灰袍巫師甘道夫，壹個向導，在環的歷史學習和建議佛羅采取從夏爾的戒指了。佛羅葉，以他的園丁和朋友，Samwise（“山姆大叔”）蓋濟，和兩個堂兄弟，Meriadoc（“歡樂”）Brandybuck和佩雷格林（“皮平”）註意到，來幫助他。
他們遇到戒靈，而仍然在希雷，但擺脫了貫穿老森林，他們在那裏的神秘和強大的性格湯姆龐巴迪資助的追求。巴羅通過後與湯姆的幫助下起伏，他們停止了在布雷鎮夜晚。他們在那裏會見阿拉貢誰通話
擰自己“行客”，並加入為指導，保護他們。他們離開布雷狹義逃脫後的戒靈的攻擊。在前往瑞文戴爾之旅，佛羅多是受傷Weathertop的戒靈，誰繼續保持密切的追求。在布魯伊能，佛羅多等人獲救福特，由埃爾隆德，在瑞文戴爾的主人，控制洪水站起來壓倒戒靈，掃他們離開。
佛羅恢復下艾隆德照顧。安理會的埃爾隆德在很大程度上揭示索倫和戒指，再加上咕嚕已逃離幽暗密林和索倫已損壞的向導薩魯曼新聞重大的歷史。理事會決定，對索倫的威脅太大，認為最好的辦法就是摧毀環。
這可以返回只有在魔，它的末日裂縫的地方是偽造的。佛羅誌願者采取戒指，以及對環“獎學金”是選擇陪他。該獎學金是由九名成員組成，從而抵消九戒靈了。隨著佛羅多，山姆，快樂和皮蓬去阿拉貢，甘道夫，吉姆利-日
格洛因兒子的位置，認為他追求的陪同下，萊古拉斯-壹位來自幽暗密林林地領域精靈，壹個人比爾博矮人-博羅米爾管家德內瑟的兒子從剛鐸領域之壹。
該公司被迫穿越他們身在何處的獸人攻擊摩瑞亞，地雷。甘道夫和炎魔戰鬥壹成屬於深的鴻溝，在他人逃生，並在洛絲蘿林精靈森林避難。隨著小艇和凱蘭崔爾夫人的禮物，這家公司卻滑下河安杜因偉大的阿蒙漢。
有博羅米爾屈從於魔戒並試圖從佛羅多，誰打破了獎學金，並繼續向魔的跋涉伴隨著三只它的誘惑。
獸人發出薩魯曼和索倫攻擊，綁架和殺害博羅米爾快樂和皮平。阿拉貢，金靂和萊戈拉斯努力將羅漢的獸人。快樂和皮平逃離時被殺害的獸人的Rohirrim和森林法貢森林找到自己喜歡交朋友，他們已廢除的樹。阿拉貢，金靂和萊戈拉斯遇到甘道夫，誰是現在“甘道夫白皮書”在法貢森林森林。
甘道夫旅遊與他們振奮希優頓，國王的羅漢，以及Rohirrim采取反對薩魯曼的軍隊的立場。希優頓最初決定努力爭取在河河渡口的福特薩魯曼的力量，但壹聽到那些誰維護該地區已經撤退到了頭盔的深處，他決定讓他站在那裏堡壘
大腸桿菌甘道夫搭乘伊森戈德;而勒茍拉斯，金靂和阿拉貢與希優頓和他的侄子伊歐墨旅遊。經過多次在頭盔的深戰鬥，最後Rohirrim安裝費和驅動獸人成為壹個由經濟需求測試，他們消失，提出Huorns森林就像甘道夫到達。
破壞的經濟需求測試艾辛格薩魯曼的殘余勢力。甘道夫，希優頓等人到達艾辛格。薩魯曼，但是，拒絕見他的方式錯誤，甘道夫剝奪了他和他的排名大部分權力，以及經濟需求測試監禁他。皮平看起來到帕蘭蒂爾，壹看到石的索倫使用了溝通薩魯曼，
不知不覺中導致索倫認為薩魯曼已經吸引了環旗手。甘道夫需要皮蓬的剛鐸刪除從帕蘭蒂爾誘惑他。
佛羅多和山姆捕獲咕嚕，迫使他引導他們魔。他們長途跋涉而艱難的道路，簡略博羅米爾的弟弟，法拉米爾資助。咕嚕背叛由領先的西力斯昂哥隧道他偉大的蜘蛛舍羅佛羅。佛羅留下了舍羅的咬昏迷
但她從三打架使用斯汀以及從?arendil的恒星的光瓶-凱蘭崔爾的夫人的禮物之壹。三，相信佛羅多死了，需要的戒指，和佛羅多是由獸人的西力斯昂哥塔。
索倫開始後，剛鐸的軍事進攻，與巫巫王，九戒靈最大，指揮戰鬥索倫的軍隊。
甘道夫到達的那斯提力斯市在剛鐸與皮平，提醒即將發生的攻擊管家。皮平成為了那斯提力斯城堡衛隊之壹，而快樂，誰在羅漢依然存在，成為紳士其國王。阿拉貢是通過死者的路徑金靂和勒茍拉斯，他提出了壹個宣誓不死軍隊的奇觀。
這些幫助他戰勝南部剛鐸的昂巴海盜的軍隊，使該地區的部隊行駛到了那斯提力斯在其圍攻援助。
德內瑟，剛鐸的執政管家，相信他的兩個兒子已經死亡，並根據索倫通過另壹個帕蘭蒂爾的影響，失去希望和自殺。但是，隨著羅漢的騎兵和阿拉貢的生力軍，是索倫的軍隊及時的援助很大壹部分被否決。國王希優頓在戰鬥中死亡，而是戒靈，女巫巫王的主，
是被殺害的伊奧雯和快樂。
三救，從囚禁佛羅多，他們透過魔的方法。經過許多困難，他們到達山毀滅。同時，在在魔的極大，人數超過了剛鐸和羅漢聯盟對抗索倫的軍隊拼命戰鬥黑門高潮，在轉移索倫的註意力從末日山的意圖，
其中佛羅必須達到以摧毀環。
在裂縫的毀滅的邊緣，佛羅落到了魔戒的誘惑，並聲稱自己了。他把他的手指上的戒指。咕嚕鬥爭與佛羅多的戒指，和叮咬過佛羅多的手指，戒指和所有，但在這樣做時，他落入了火，與他壹起參加環。午夜兇鈴因此unmade的唯壹方式可以是：在同壹火警，是偽造的。
在其毀滅瞬間，索倫亡，他的軍隊土崩瓦解，在黑暗塔進入灰塵，戒靈瓦解，以及環戰爭壹旦崩潰結束。
壹片勝利慶祝活動，阿拉貢是剛鐸國王加冕，他結婚阿爾溫，在埃爾隆德的女兒和他長時間的愛。
薩魯曼逃離他Orthanc關押和奴役夏爾，但返回的哈比人提出叛亂，推翻的他拜沃特戰役。薩魯曼的喉嚨是由Wormtongue縫，他的前仆人，誰是又與哈比弓箭箭頭砍伐。快樂和皮蓬是被譽為英雄。三使用來自加拉迪爾他的禮物，以恢復和美化希雷，
結婚羅西和棉花。佛羅仍然受傷的身體和精神，並通過比爾博和甘道夫，從灰海文斯在西帆的不死之靈地的陪同下尋求和平。三回到家中，並最終成為夏爾市長。羅西後去世，留給他的三女兒的Westmarch紅皮書，穿越的海面上，環的最後承擔者西